Adjustable arm

ABSTRACT

An adjustable arm having a joint (17,19) at each end with a push rod (35) extending axially through the arm with each end of the rod bearing against one of the components (23,45) of the adjacent joint and means (31) for applying a compressive force to the push rod and thereby simultaneously lock both joints against relative movement.

This invention relates to an adjustable arm and in particular to an armconsisting of a plurality of arm sections disposed in end to endrelation with adjacent arm sections interconnected for angular movementtherebetween about at least one axis.

Adjustable arms of the type to which this invention relates arewell-known. In many situations, it is necessary to lock the arm sectionsagainst angular movement to restrain the arm from movement out of aposition into which it has been adjusted. To accomplish this,conventional adjustable arms are commonly provided with a lockingmechanism at each joint between adjacent arm sections. However, such anarrangement has a disadvantage in that it is necessary to operate thelocking mechanisms individually to lock the arm in the desired positionand to release the arm to allow for further adjustment of the armsections. This may be a time consuming and tedious operation, especiallyif adjustments to the arms position are required to be carried outregularly.

It is an object of the present invention to overcome the above-mentioneddisadvantage by providing an adjustable arm in which the arm sectionsare able to be locked against angular movement in one operation.

Broadly the invention resides in an adjustable arm having a joint ateach end capable of movement about at least one axis, a push rodextending axially along the arm with each end in contact with one of thecomponents of the adjacent joint and means for applying a compressiveforce to the rod, thereby simultaneously locking both joints againstrelative movement.

More particularly the invention resides in an adjustable arm comprisingan intermediate arm section and a pair of end arm sections disposed oneat each end of the intermediate section, a joint connecting each endsection to the respective end of the intermediate section for angularmovement therebetween about at least one axis, each joint having a firstpart attached to the intermediate section and a second part attached tothe respective end section, a push rod extending axially along theintermediate section with the respective ends of the push rod locatedagainst said second parts of the joints, and means for effectingrelative movement between the intermediate section and the push rodbetween a first position in which the ends of the push rod are insliding engagement with the respective second parts of the joints and asecond position in which the ends of the rods are in frictionalengagement with respect to said second parts.

According to a preferred feature of the invention each joint is either aball and socket type joint or a knuckle joint.

The invention will be better understood by reference to the followingdescription of two specific embodiments thereof as shown in theaccompanying drawings in which:

FIG. 1 is a sectional elevation of an adjustable arm according to thefirst embodiment; and

FIG. 2 is a sectional elevation of an adjustable arm according to thesecond embodiment.

Referring to FIG. 1 of the drawings, the adjustable arm according to thefirst embodiment comprises an intermediate arm section 11 and a two endsections 13 and 15, one at each end of the intermediate section. A joint17 couples one end of the end section 13 to the adjacent end of theintermediate section 11. Similarly, a joint 19 couples one end of theend section 15 to the adjacent end of the intermediate section.

The end section 15 is in the form of a base which is adapted formounting on a suitable structure such as a workbench, or a stand whichmay be either portable or fixed in position. The free end of the endsection 13 is adapted to support an object such as a clamp (not shown)which may require positional adjustment after attachment to the endsection 13.

The joint 17 is in the form of a knuckle joint comprising a fork 21integral with the intermediate section 11 and an eye 23 mounted on theend section 13. The fork 21 and eye 23 are united by a pivot pin 25. Thejoint permits relative angular movement between the end section 13 andthe intermediate section 11 about the central longitudinal axis of thepin 25.

The joint 19 is of the ball and socket type, the ball 27 being fixed tothe intermediate section 11 and the socket 29 being formed integral withthe end section 15. The ball 27 is retained in the socket 29 by means ofa collar 31 threadedly engaged to the end section 15. The collar 31 isformed with an inturned flange 33 which engages the ball 27.

A push rod 35 is slidably received in an axial passage 37 in theintermediate section 11 and an aligned passage 39 in the ball 27. Theend of the push rod 35 corresponding to the ball 27 is formed with anenlarged section 39 which is located in a corresponding enlarged section41 in the passage 37. The free end 43 of the enlarged section 39 islocated against the concave face 43 of the socket 29 and is shaped toconform with the concave face 43. The other end 47 of the push rod islocated against the eye 23 of the joint 17. There is a clearance space49 between the outer face of the ball 27 and the concave face 43 of thesocket 29.

Rotation of the collar 31 in the direction which causes it to move inthe direction towards the end section 15, urges the ball 27 towards theconcave face 45 of the socket, thereby reducing the size of theclearance space 49. The effect of this is that respective ends of thepush rod are forced into frictional engagement with the socket 29 andthe eye 23. In this way, the joints 17 and 19 are locked so as not topermit angular movement between their respective arm sections.

The embodiment shown in FIG. 2 of the drawings is similar to that shownin FIG. 1 and the same reference numerals are used to identifycorresponding parts. In this embodiment the joint 17 is of the ball andsocket type to permit angular movement between the arm sections 11 and13 about a multitude of axes rather than about one axis as was the casewith the knuckle joint of the first embodiment.

The joint 19 is of a ball and socket type. The ball 27 is formed in twoparts; one part 51 is integral with or fixed to the intermediate section11 and the other part 53 is integral with or fixed to the push rod 35.The part 53 locates against the concave face 45 of the socket 29. Aclearance space 55 is provided between the ball parts 51 and 53 and aclamping mechanism 57 is provided to selectively move the ball part 51towards the ball part 53 and thereby reduce the size of the clearancespace. The effect of this is that the ball part 53 at one end of thepush rod is forced into frictional engagement with the socket 29 and theother end 47 of the push rod is forced into frictional engagement withthe ball of the joint 19.

The clamping mechanism 57 includes a collar 59 surrounding the part 51of the ball 27, and a releasable clamping device 61 which is adapted tourge the collar into engagement with the part 51 and thereby effect thelocking action.

From the foregoing, it is evident that the present invention provides anadjustable arm in which the arm may be adjusted to any angular positionand locked in that position, the locking operation requiring only onelocking action.

It should be appreciated that the scope of the invention is not limitedto the scope of the embodiments described; for example, although theembodiments described have only three arm sections, an adjustable armaccording to the invention may be provided with any suitable number ofarm sections.

The claims defining the invention are as follows:

I claim:
 1. An adjustable arm having a knuckle joint at one end and aball and socket joint at the other end, a push rod extending axiallyalong said arm and slidably mounted therein, one end of the rod bearingagainst the eye of the knuckle joint and the other end of the rod beingagainst the socket of the ball and socket joint and means for applying acompressive force to said rod comprising a collar screwed onto thesocket over the ball for simultaneously locking both joints againstrelative movement.
 2. An adjustable arm as claimed in claim 1 whereinpart of one of the joints forms a base through which the arm may bemounted on a suitable structure.
 3. An adjustable arm comprising anintermediate arm section and a pair of end arm sections disposed one ateach end of the intermediate section, a joint connecting each endsection to the respective end of the intermediate section for angularmovement therebetween about at least one axis, each joint having a firstpart attached to the intermediate section and a second part attached tothe respective end section, a push rod extending axially along theintermediate section with the respective ends of the push rod locatedagainst said second parts of the joints, and means for effectingrelative movement between the intermediate section and the push rodbetween a first position in which the ends of the push rod are insliding engagement with the respective second parts of the joints and asecond position in which the ends of the rods are in frictionalengagement with respect to said second parts, one of said jointscomprising a knuckle joint and the other of said joints comprising aball and socket joint, one end of said rod bearing against the eye ofsaid knuckle joint and the other end of said rod being against thesocket of said ball and socket joint, said means for applyingcompressive force to said rod is a collar screwed on to the socket oversaid ball.
 4. An adjustable arm as claimed in claim 3 wherein theintermediate arm section is tubular and the push rod is slidably mountedtherein.
 5. An adjustable arm as claimed in claim 3 wherein part of oneof the joints forms a base through which the arm may be mounted on asuitable base.
 6. An adjustable arm as claimed in claim 3 wherein theball has an enlarged bore therein larger in diameter than the rod andthe rod is operably engaged with a cylindrical portion contained withthe bore and adapted to engage the socket upon the application of acompressive force.